Wait for cloud-init to complete before pkg cache is updated

[trstringer]

What this PR does / why we need it: This makes the cluster provisioning wait until cloud-init configuration has completed prior to updating the cache. A part of the cloud-init configuration includes adding apt source (templating), and it appears as though there was a race condition causing transient failures (for more information, please see #3204).

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #3204

Special notes for your reviewer:

If applicable:

• documentation
• unit tests
• tested backward compatibility (ie. deploy with previous version, upgrade with this branch)

Release note:

Fix race condition for pkg cache updating prior to cloud-init completion

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[jackfrancis]

@trstringer Thanks! Your analysis is probably spot on! We already have #3230 gathering test data, and it accomplishes the same thing (in another way, by moving the apt-get update into a func that is invoked after cloud-init)

[trstringer]

@jackfrancis ok cool, thanks!!